Post prandial (PP) Blood Sugar Test: Is It 1.5 Hours or 2 Hours After Food?
Patient's Query
I already know that pp blood sugar means checking sugar after food, usually after two hours. But when I go to many labs, they casually tell me to come after one and a half hours. Even on some lab reports, it is written as “1½ hour PP sugar.” This is confusing me.
On the internet, forums, and even YouTube videos, different timings are mentioned. Some say 90 minutes is fine, others insist on two hours. I also noticed that many people include the time taken to eat breakfast, around 20 to 30 minutes, and then calculate from there.
So what is the correct timing actually? Is there really a big difference between one and a half hours and two hours? If labs are doing 1.5 hours, is it acceptable or wrong? I want clarity so that my reports are accurate and meaningful for my diabetes control.
Endocrinologist Answers
This is a very common and very valid confusion. Let me clarify it clearly.
The correct and standard postprandial blood(PP) sugar test is done exactly 2 hours after the start of the meal.
This is not a random number. It is based on physiology and long-standing diabetes guidelines.
Now, where did the 1.5-hour practice come from, especially in India?
In real life, many people take:
- 15 to 30 minutes to finish breakfast
- Labs often assume this eating time as part of the “two hours”
- So they tell patients to come 90 minutes after finishing food, thinking it equals two hours from starting the meal
Over time, this practical shortcut slowly became routine and got written casually as “1½ hour PP sugar.” But medically, this creates a problem.
Here is why:
- Blood sugar usually peaks between 60 to 90 minutes
- By 2 hours, insulin action should bring sugar down
- Testing at 1.5 hours often shows higher values than true 2-hour levels
- This can falsely suggest poor control or lead to unnecessary treatment changes
What is the correct method you should follow?
- Check fasting sugar
- Take your usual morning diabetes medicines or insulin
- Start your breakfast
- Exactly 2 hours after the first bite of food, check postprandial sugar
Do not count from when you finish eating. Do not shorten the time.
Is 30 minutes difference significant?
Yes. Clinically, it can matter, especially when:
- Diagnosing diabetes
- Adjusting medications
- Evaluating post-meal spikes
- Comparing reports over time
Practical advice:
- Always aim for 2 hours after starting the meal
- Be consistent with timing every time
- If a lab insists on 1.5 hours, inform your doctor so results are interpreted correctly
Consistency is more important than convenience.
Bottom line
- Postprandial blood sugar means 2 hours after starting the meal, not 1.5 hours. The shorter timing became common due to practical habits, not medical accuracy.
- For meaningful diabetes management, always stick to the true 2-hour rule and discuss results with your treating doctor.
References:
- https://diabetesjournals.org/care/issue/49/Supplement_1
- https://iris.who.int/server/api/core/bitstreams/ef6a81ae-5db3-4c5c-9136-c047bd8f8344/content
- https://idf.org/what-we-do/education/idf-clinical-practice-recommendations-for-type-2-diabetes-2025/
- https://diabetesjournals.org/care/article-abstract/26/3/881/29237/Contributions-of-Fasting-and-Postprandial-Plasma
Disclaimer: The information provided in this Q&A is for educational purposes only and should not be considered as medical advice. Always consult with a qualified healthcare professional for personalized medical guidance and treatment recommendations.